Cements of various types have been employed for thousands of years in all manner of construction. Typical modern hydraulic cement, most commonly known as ordinary Portland cement (OPC), is one of the most consumed substance on the planet.
Though ordinary Portland cement based concretes have a lower CO2 footprint than most other structural materials, the sheer volume of Portland cement concrete produced every year makes it a significant contributor to global anthropogenic carbon dioxide emissions. In order to reduce global CO2 emissions it is necessary to adopt new approaches to create a new generation of hydraulic cements. Today, the most efficient cement kiln can produce cement clinker with an associated emission of 816 kg of CO2 per ton of OPC clinker. Blending the ground cement clinker with supplementary cementitious materials (SCM) which have low or zero associated production CO2 emissions reduces the total embodied CO2 of the final product. Using a cement with the lowest possible clinker factor for a given application is the most common industry approach to reducing the CO2 footprint of concrete installations.
The SCMs blended with OPC clinker to obtain a low clinker factor are mainly fly ash and slag. Given the drive to reduce the CO2 footprint through a reduction in cement clinker factor, the demand for what were previously considered waste materials (fly ash and slag) has increased to the point where the costs of these materials can be comparable to OPC. Due to this demand for substances previously considered waste products as well as minimally processed waste oil shales or clay minerals can be economically produced and utilized as SCMs.
There is a need for sustainable SCMs that can be produced and replace OPC significantly in concrete.